"If you really do need to build thread-safety yourself, do it in an encapsulated way, eg with all the multi-threaded management of access and updates to your data structures hidden behind class APIs so that fixes can be applied internally with no need for the external users to have to change their usage"

"Caches losing a small percentage of data can mean a large increase in datstore load (eg 95% hit ratio dropping to ->90% means that DB load goes from 5%->10% - a doubling of load; the same 5% drop from 99.5%->94.5% means that DB load goes from 0.5%->5.5% - a 10x increase in DB load)"